Preparation and characterization of pesticide Fosthiazate‐loaded microcapsules for controlled release system

Preparation of Fosthiazate (FTZ)‐loaded microcapsules with controlled release was attempted by the interfacial polymerization using toluene diisocyanate (TDI) and triethylenetetramine (TETA) as monomers. The effects of the monomer concentration and the monomer concentration ratio on characteristics of the microcapsules such as size, shell thickness and release behavior in water and in soil were studied. In the study, FTZ was successfully encapsulated into a polyurea resin, and the characterization revealed that the microcapsule shell became thicker proportionally to the applied monomer concentration. The release rate of FTZ from the microcapsules in water was mostly proportional to the ratio of the surface area to the shell thickness of the microcapsules, and the release rate fitted the first‐order kinetic model. On the one hand, when TDI concentration was low or the monomer concentration ratio was high, the release rate was significantly increased owing to the formation of insufficient microcapsule shell and the coarseness of the shell. Moreover, the slower the release rate in water was, the higher residual ratio of FTZ in soil could be maintained. However, it was also observed that the release rate in soil was faster than that in water. It is suggested that the constant replacement of water around the microcapsules accelerated the release rate, or the microcapsule particles migrated through the soil. These results indicated that FTZ‐loaded microcapsules with controlled release were able to be prepared. In addition, basic findings about the relationship and the difference between the release behaviors of FTZ‐loaded microcapsules in water and in soil were obtained.